Under the limited investment budget, the best project combination problem is investigated for multiple distribution network projects with a high penetration new energy to achieve the highest reliability and economy. Considering the difference of marginal benefit of reliability in different power supply areas and the complex correlation between projects, an optimization model is proposed for the distribution network planning project. Firstly, the characteristics of benefit coupling and time series correlation are taken into account to establish the project benefit coupling equation. On this basis, the project benefit coupling characteristics are extracted. Secondly, the association characteristics of project time series are determined according to the definition of time series association rules. The relationship between distribution network planning projects are defined, and the constraints of distribution network planning projects are designed. Then, the optimization model is established to maximize the project investment benefit. In the end, two existing methods are compared and verified. It is shown that the proposed model is low in cost and high in benefit. It also provides a basis for the optimization of distribution network multi-area projects under limited budget.